The present invention is generally directed to a heat pipe apparatus and method used in heating, refrigeration, and air conditioning systems. More particularly, the present invention is directed to an apparatus and method employing a controllable heat pipe apparatus that provides a more energy efficient heating, refrigeration, and air conditioning systems.
Air conditioning and heating systems generally require the transfer of heat to either cool or heat the air to a comfortable temperature. A heat pipe is one of the most efficient systems in use today for transferring heat. Heat pipes are vessels that contain a precise amount of a working fluid and have at least two sections, an evaporator section and a condenser section, that exchange heat with the environment external to the heat pipe. The evaporator section is disposed in thermal communication with an external heat source, while the condenser section is disposed in thermal communication with an external heat sink. Further, the heat pipe also has an adiabatic section that connects the evaporator section to the condenser section and through which heat is transferred within the heat pipe from the evaporator section to the condenser section.
Within the evaporator section of a heat pipe, the working fluid begins in its liquid state. As a heat source such as ambient hot air transfers heat by conduction through the heat pipe""s external surfaces to the liquid that is the working fluid, the temperature of the liquid rises steadily commensurate with the provision of heat. This temperature rise continues until the temperature of the liquid attains the temperature at which the liquid evaporates to form the vapor state of the working fluid. At this vaporization temperature, the provision of additional heat to the liquid transforms the liquified working fluid into vaporized working fluid vapor pressure drives the vaporized working fluid through the adiabatic section to the condenser section of the heat pipe. At the condenser section, the vaporized working fluid transfers the heat absorbed in the evaporator section to the heat sink located at the condenser section of the heat pipe, thereby transforming the vaporized working fluid back into its liquid state. Capillary action and/or gravity return the liquified working fluid back to the evaporator section. The heat pipe continues the process of transferring heat as long as there is a temperature differential between the heat pipe""s evaporator section and condenser section or a control technique interrupts the heat transfer process.
Controllable wrap around heat pipes that are installed,in air handlers of buildings are well-known. Some of these heat pipes use banks of individual tubes that can be tilted for control purposes. Still another type uses vertical tubes and headers with valving for control purposes. In these applications, the heat pipes are positioned such that the evaporator section is located amidst a heat source and the condenser section is amidst a heat sink.
However, known heat pipes are difficult to manufacture. The tilt-controlled heat pipes require the processing (evacuating and charging) of each individual tube. Sealing of the air passageways in the areas that the heat pipe tilts, is also difficult. In terms of performance, there are limitations to the length of the tubes to maintain desired capacities.
In the vertical tube/headered heat pipe, there are limitations to the vertical length of the tubes for performance. The manufacturing of such heat pipes requires precise spacing of the holes in the manifolds and numerous connections of the tubes into the manifold. Each connection of the tubes into the manifold requires a brazing operation. In addition, it is very difficult to align the headers of different sections within an evaporator or condenser section of a heat pipe.
Moreover, heat pipes that perform more efficiently are desired. Accordingly, a need currently exists for an improved heat pipe that overcomes manufacturing difficulties while enhancing performance for application to heating, refrigeration and air conditioning systems.
The present invention recognizes and addresses the foregoing disadvantages, and others of prior art constructions and methods. Accordingly, a primary object of the present invention is to provide an improved heat pipe apparatus suitable for controlling air temperature in heating, refrigeration, and air conditioning systems.
Another object of the present invention is to provide an improved, controllable, wrap-around heat pipe for controlling air temperature in heating, refrigeration, and air conditioning systems.
A further object of the present invention is to improve the efficiency of heat transfer within the adiabatic section of a heat pipe apparatus by providing a heat exchanger that controls the temperature of the working fluid within the adiabatic section of the heat pipe apparatus.
Yet another object of the present invention is to further improve the efficiency of an heat pipe apparatus and method for controlling air temperature in heating, refrigeration, and air conditioning systems by providing mechanisms for controlling the flow of fluids through the heat exchanger.
Still another object of the present invention is to provide a heat pipe apparatus for controlling air temperature in heating, refrigeration, and air conditioning systems without any height restriction for the tubes of the heat pipe. A still further object of the present invention is to provide a heat pipe apparatus for controlling air temperature in heating, refrigeration, and air conditioning systems, wherein the heat pipe employs longer continuous, machine formed tubes that require up to 75% fewer brazing operations and only one evacuation and charging process during manufacture of the heat pipe.
These and other objects of the present invention are achieved by providing a more energy efficient apparatus and method suitable for controlling air temperature in an air passage of air conditioning, refrigeration, and heating systems. The apparatus and method preferably employs a primary heat transfer unit and a secondary heat transfer unit. The primary heat transfer unit includes a primary fluid that functions as the working fluid flowing therein. The secondary heat transfer unit preferably employs a heat pipe that includes a secondary fluid that functions as the working fluid flowing therein.
In a presently preferred embodiment of the present invention, the heat pipe includes an evaporator section, a condenser section, and an adiabatic section, and the secondary fluid flows through each section. The condenser section and evaporator section of the heat pipe of the present invention are connected by at least one interconnected loop such that the secondary fluid can flow continuously throughout the system.
In one embodiment of the present invention, air flowing through the air passage of the apparatus thermally communicates with the heat pipe""s evaporator section, which precools the air before the air thermally communicates with a primary heat transfer unit in the form of a cooling unit. In the heat pipe""s evaporator section, the secondary fluid is transformed into vapor and the vaporized secondary fluid flows to the condenser section through the adiabatic section. In the heat pipe""s condenser section, vaporized secondary fluid is condensed back to its liquid state, thereby transferring most of the heat absorbed in the evaporator section to air that is thermally communicating with the condenser section.
In accordance with the present invention, an adiabatic section that connects the heat pipe""s evaporator and condenser sections is specially configured and equipped to provide finer control over the amount and rate of heat transfer permitted to occur within the heat pipe. In one embodiment of the present invention, the adiabatic section is provided in the form of a shell-and-tube heat exchanger that is positioned between each pipe""s evaporator section and condenser section. A primary coolant flows through the heat exchanger to affect the temperature of the secondary fluid flowing there through. In one air conditioning embodiment, the primary coolant is chilled water, and in another embodiment for heating systems the primary coolant is hot water.
Further control of the heat pipe is provided by primary and secondary flow control devices in accordance with the present invention. In one embodiment, a flow control valve is configured and disposed to control the flow of primary coolant (chilled water or hot water) into the shell-and-tube heat exchanger. In another embodiment, another flow control valve is configured and disposed to control the flow of secondary fluid within the shell-and-tube heat exchanger. The use of these flow control devices further enhances the performance of the adiabatic section of the pipe.
Other objects, features and aspects of the present invention are discussed in greater detail below.